Up-conversion luminescence in Yb3+/Er3+ co-doped ZnGa2O4 and ZnAl2O4 powder phosphors

ZnGa2O4:Yb3+,Er3+ and ZnAl2O4:Yb3+,Er3+ up-conversion powder phosphors with different Yb/Er ratio are synthesized by solid-state method and subsequent thermal treatment at 1300 ℃, which can generate strong up-conversion emissions in visible spectral range under 980 nm excitation. For the as-prepared ZnGa2O4:Yb3+,Er3+ phosphors, the green and red emissions around 524 nm (corresponding to 2H11/2 → 4I15/2 transition of Er3+), 549 nm (corresponding to 4S3/2 → 4I15/2 transition of Er3+) and 659 nm (corresponding to 4F9/2 → 4I15/2 transition of Er3+) indicate the optimal Yb/Er ratio for the sample is 7/1, while the ZnAl2O4:Yb3+,Er3+ phosphors with the same green and red emissions is Yb/Er = 3/1. Besides the up-conversion luminescence, the morphology and crystal structure are also investigated. All ZnGa2O4:Yb3+,Er3+ powders contain regular long rods with diameter of about 600-900 nm, while agglomerates composed of nonregular particles with size about 200-400 nm are shown in all ZnAl2O4:Yb3+,Er3+ powders. Additionally, all samples are spinel structure with a high degree of crystallinity. Consequently, the particles of moderate size, stable crystal structure and enough high intensity of green and red emissions in all ZnGa2O4:Yb3+,Er3+ and ZnAl2O4:Yb3+,Er3+ powder phosphors endow them potential applications in infrared detection, display devices and so on.